1. Field of the Invention
The present invention relates to an outboard engine structure detachably mounted at the stern of a boat or ship for propelling the same, and more particularly, to an exhaust system for an engine mounted on the outboard engine structure.
2. Description of the Prior Art
In general, an outboard engine structure is constructed such that an engine having a crankshaft disposed vertically therein is mounted at an uppermost portion of an outboard engine structure body case whose lower portion is submerged in water. An output from the engine is transmitted to a propeller shaft through a drive shaft provided in a suspended manner within the engine body case to rotate the propeller, as described in, for example, Japanese Utility Model Application Laid-Open No. 93597/76.
Exhaust gas from the engine is passed through an exhaust passage located vertically within the engine body case, into a lower portion of the case and discharged into water.
In such an outboard engine structure, if an exhaust emission control catalytic converter is mounted in an exhaust system for purification, it is difficult to place and support the catalytic converter, because the exhaust passage is located within the engine body case, as described above, and the engine body case is formed into a narrow configuration in order to reduce the underwater resistance of the submerged portion of the engine body case and to reduce the weight of the engine body case.